package com.xunfang.shareaddress.method;

public class MathMethod {
	// 计算地球上两点间的距离
	private static final double EARTH_RADIUS = 6378137;

	private static double rad(double d) {
		return d * Math.PI / 180.0;
	}

	public static double GetDistance(double lng1, double lat1, double lng2,
			double lat2) {
		double radLat1 = rad(lat1);
		double radLat2 = rad(lat2);
		double a = radLat1 - radLat2;
		double b = rad(lng1) - rad(lng2);
		double s = 2 * Math.asin(Math.sqrt(Math.pow(Math.sin(a / 2), 2)
				+ Math.cos(radLat1) * Math.cos(radLat2)
				* Math.pow(Math.sin(b / 2), 2)));
		s = s * EARTH_RADIUS;
		s = Math.round(s * 10000) / 10000;
		return s;
	}

	// 计算平面上两点间的距离
	public static double flatDistance(double x1, double y1, double x2, double y2) {
		double x = x1 - x2;
		double y = y1 - y2;
		double flat_distance = Math.sqrt(x * x + y * y);
		return flat_distance;
	}
}
